Are artificial sweeteners really bad for you?

If you're a fan of the clean eating movement, and prefer to enjoy foods in their natural state, you probably steer clear of artificial sweeteners. While the likes of aspartame and sucralose contain zero calories – making them an appealing option for those who are watching their weight – you're unlikely to find today's healthy eating gurus knocking back a Diet Coke.

In fact, with so many scare stories circulating, it can be hard to know what to believe. Over the years, artificial sweeteners have garnered a bad rap, having been associated with everything from gastrointestinal issues to cancer.

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So what's the truth – are artificial sweeteners a safe and sensible alternative to sugar? Or should you think twice before purchasing that sugar-free chewing gum?

Artificial sweeteners are safe for most people

If you live in Europe, all the artificial sweeteners you consume are tested and regulated by the European Food Safety Authority (EFSA), which sets acceptable daily limits. These limits tell you the maximum amount considered safe to consume each day, over the course of a lifetime.

"Artificial sweeteners are subject to robust testing and the advisable daily limits are much higher than would ever be consumed. The EFSA carried out a large scale review of sweeteners in 2013 and concluded they are safe, including for pregnant women and children over 12 weeks of age."

The occasional can of diet drink is therefore not a problem. Because the limits are so high, a 70kg man would have to drink at least 14 cans a day, every day, to incur any health risks from the artificial sweetener itself.

Some people should be careful

These recommendations exclude one small subset of people: namely those suffering from the rare genetic disorder Phenylketonuria (PKU). PKU sufferers cannot break down the compound phenylalanine, and therefore should not consume aspartame. However, this applies to less than 1 in every 10,000 people.

A more common reason to exercise caution might be irritable bowel syndrome (IBS). For some people with IBS, eating too much xylitol (a sweetener in chewing gum and mints) can lead to diarrhoea or bloating. On top of that, if you're allergic to sulfonamides, you should avoid saccharin, as it can cause breathing difficulties, rashes and diarrhoea.

They don't cause cancer

On a more positive note, the myth that artificial sweeteners cause cancer has now been solidly debunked. According to Cancer Research UK: "Large studies looking at people have now provided strong evidence that artificial sweeteners are safe for humans."

The myth first arose in the 1970s when studies on lab rats linked saccharin with the development of bladder cancer. These findings were so concerning that, until the year 2000, all food containing saccharin in the US was required to carry a warning label. Further testing, however, revealed that these findings were only applicable to rats and mice and had no relevance to people.

Another sweetener, aspartame, came under scrutiny in the 1990s, when a paper suggested it might be linked with brain tumours. However, a later study, involving nearly 500,000 people, found no connection at all.

"A number of large scale scientific reviews have discredited this link and there are no grounds to associate consumption of artificial sweeteners with increased cancer risk," says Clare.

The link with weight is not clear-cut

Whether or not artificial sweeteners can help you lose weight is more contentious. On one hand, since they are calorie free, they can be useful in reducing overall energy consumption. On the other hand, a number of studies have actually associated them with weight gain.

Clare says:

"Weight gain has been suggested as a side effect of consumption of artificial sweeteners, diet drinks in particular. A number of hypotheses have been put forward for this, including artificial sweeteners failing to activate the 'food reward pathway'. This would mean the craving for sweet foods continues, and more food and larger portions are consumed."

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She points out, however, that the link is mainly based on observational studies, and does not take account of other factors such as overall calorie consumption. After all, swapping sugary drinks for diet ones won't help you lose weight if you offset the difference with a doughnut.

While a small number of studies have linked sucralose and saccharin with increased levels of insulin production – possibly due to changes in gut bacteria – the jury's out on how artificial sweeteners affect your blood sugar. So far, the evidence is not sufficiently robust to say.

Not all sweeteners are made alike

If you've been trying to avoid artificial sweeteners, you may be familiar with a natural alternative, namely stevia. Derived from the stevia plant, this sweetener is around 200 times sweeter than sugar, while remaining calorie-free. It was approved in the US in 2008, and in Europe in 2011, and has become steadily more popular ever since.

Some studies have suggested that stevia might have health benefits. As Clare explains:

"Stevia has been shown to reduce blood pressure in individuals with high blood pressure, but this benefit is only seen when blood pressure is very high, and when higher doses than would generally be consumed are taken. Stevia has also been linked with increased insulin sensitivity, which is helpful in people with type 2 diabetes. There have been claims that stevia can reduce cholesterol, but high doses were used and the research was carried out in rats, so not necessarily transferable to humans."

However, some consumers have complained of a bitter or licorice-like aftertaste, meaning it may not be a true substitute for sugar. A number of products containing stevia are sweetened with sugar too.

The verdict

So what does all this mean for your Diet Coke habit? On balance, the evidence suggests that most people can consume these products in fairly substantial quantities, without any risk to their health.

That said, scientists still don't know exactly how artificial sweeteners affect your body, especially in terms of regulating weight. Most likely, that Diet Coke is still better for you than the full sugar version. But if you want to err on the side of caution, it may be best to reach for a glass of water instead.

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